The paper describes the methodology used in the groundwater resource estimation and the results of the latest country-wide assessment. In India, dynamic groundwater resources are estimated jointly by the Central Ground Water Board (CGWB) and State governments at periodic intervals. The latest estimates of dynamic resources are based on groundwater resource estimation methodology-1997 (commonly known as GEC-1997). These estimations are widely used in formulating various groundwater development and management plans. The paper also discusses future strategies on groundwater resource estimations.

The methodology for the assessment comprises of water-level fluctuation technique and empirical norms for recharge estimation. The basic principle followed in this methodology is the estimation of annual groundwater recharge from rainfall and other sources, including irrigation, water bodies and artificial recharge, determination of present status of groundwater utilization and categorization of assessment units based on the level of groundwater utilization & long-term water level trend. The stage of groundwater development is worked out and assessment units are categorized based on the stage of groundwater development and long-term water-level trend.

Groundwater over-exploitation is more prevalent in northwestern, western and peninsular India while Eastern India has good potential for future groundwater development. Considering the changing groundwater scenario, reassessment of groundwater resources needs to be carried out at regular intervals and would entail a further strengthening of the available database.

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